Vehicle Heat Research Articles

Impact of optimized gas-liquid separator on temperature and frost distribution in electric vehicle heat pump AC

In the context of low temperatures, the outdoor evaporator surface in an electric vehicle's heat pump air conditioning system tends to accumulate frost unevenly. This uneven frosting occurs due to the varying heat exchange capacity of the refrigerant's two phases within the evaporator. Any reduction in the heat exchanger's capacity would lead to a negative impact on system performance. To address these challenges, this study introduces a gas–liquid separator placed in front of the outdoor evaporator. The aim was to enhance both the outdoor evaporator's performance and the overall system efficiency while investigating frost formation and heat distribution in the outdoor evaporator within a heat pump air conditioning system. The research outcomes demonstrate that the gas–liquid separator can effectively enhance evaporating pressure by regulating the opening degree of the gas-phase bypass valve. Optimal performance is achieved with the gas-phase branch bypass valve set between 20% and 30%, ensuring a stable operational condition and higher evaporating pressure. Moreover, the incorporation of a gas–liquid separator could lead to significant improvements in system performance, with increases of 6.9% in heat capacity and 7.4% in COP observed. Additionally, this enhancement extends to the outlet air temperature, showing improvements ranging from 3.6% to 11.2%.

Potential benefit of electric vehicles in counteracting future urban warming: A case study of Hong Kong

• Warming effects by vehicle heat intensify in winter but shrink in summer in 2050 • Adopting electric vehicles can offset 25.5% of the future warming in winter • Electric vehicles provide limited cooling benefit to Hong Kong in summer • Carsharing system provides negligible cooling benefit at the city scale The global electric vehicle (EV) market is undergoing rapid expansion. EV adoption can reduce vehicle heat (VH) emissions on the road, yet its potential benefit to the urban thermal environment has rarely been investigated. In this study, we examine the cooling benefit of EV adoption and its combination with the carsharing system under future climates using numerical weather simulations. Under the worst scenario, the urban air temperature will increase by 0.90 °C in January and 1.47 °C in July by 2050 in Hong Kong. The warming effect of VH is found to intensify in winter and shrink in summer under future climates. In winter, EV adoption can offset 25.5% (0.23 °C) of the global warming signal at the city scale, and the benefit is most distinct during the evening. However, EV adoption provides less cooling in summer when the global warming signal is more evident. By saving parking spaces and converting them into outdoor green spaces, the carsharing system can provide additional cooling benefits only during the evening rush period in winter. Our results provide insights into the potential benefits of green transportation technology in urban heat mitigation.

Controlling cabin heating to improve range and battery lifetime of electric vehicles

Short range remains a major disadvantage of battery electric vehicles compared to vehicles that have combustion engines. Range reductions also result from low ambient temperatures and from battery aging. By varying power of the heating system depending on the highly fluctuating propulsion power and using electrothermal recuperation, range losses can be minimized. This paper focuses on the development and comparison of strategies to control the vehicle's heating circuit. Rule-based, fuzzy logic, and optimization-based strategies are designed and implemented in a validated BMW i3 simulation model. The results show that fuzzy logic leads to the greatest improvement of range and battery lifetime. Compared to the standard strategy, range can be increased by 14% at −10 °C and by 6.5% at 0 °C. The current throughput during recuperation is reduced the most by a rule-based strategy that prioritizes the heater. For discharging, fuzzy logic can reduce the current throughput by a maximum of 11%, which leads to a capacity fade reduction of 4.3%. Since air mass is controlled separately, the cabin temperature remains almost constant, thus maintaining the comfort of the user. • Heater power control adaptive to drive power increases range and battery lifetime. • Energy management concepts: Rule-based, Fuzzy Logic, and Optimization. • Validated BMW i3 model combines longitudinal dynamics, battery and coolant circuit. • Simple strategies show the best results and offer in-vehicle implementation. • At 0 °C, range can be increased by 6.5%, battery aging reduced by 2.1%.

Exploring the impacts of heat release of vehicles on urban heat mitigation in Sendai, Japan using WRF model integrated with urban LCZ

Studies have been conducted globally on urban heat countermeasures utilizing Weather Research and Forecasting (WRF) numerical modeling system. Yet, the effects of vehicle heat (VH) on near-surface air temperature in Japanese cities were not clarified. In this study, the WRF Building Effect Parameterization and Building Energy Model (BEP-BEM) coupled with local climate zones (LCZs) was adopted for simulating the influences of VH on the urban climate over Sendai, Japan. To do so, we proposed a novel method to estimate the hourly VH for LCZs via open-source data. Integrating VH and specific urban canopy parameters (UCPs) into BEP-BEM, the climate model was established and then validated with the observed data. Based on that, effects of various urban heat countermeasures were analyzed at a high spatial resolution. It was found that eliminating the vehicle heat contributes up to 0.12°C to urban heat mitigation, as the most effective countermeasures for the compact areas of city center. This study provided a feasible and reliable workflow to quantitatively evaluate urban heat mitigation strategies at high spatial resolution, specifically for reducing VH in Japanese cities, that can support related urban planners and decision makers for implementing targeted urban heat mitigation strategies.

Spatiotemporal impact of vehicle heat on urban thermal environment: A case study in Hong Kong

Vehicle heat (VH) is a substantial portion of anthropogenic heat and can affect the urban thermal environment. Quantifying the impact of VH has implications for the potential benefits of electric vehicles in cities, yet the spatiotemporal impact of VH has not been investigated separately. This study incorporates VH and urban landscape data into the Weather Research and Forecasting (WRF) model to estimate the VH impacts at a fine spatial resolution over Hong Kong. Results show a strong temporal variation of the VH impact at daily, weekly, and seasonal scales: 1) the warmth of urban canyon air temperature is stronger and more consistent at night than in daytime, 2) increases in sensible heat fluxes are more pronounced during weekdays than weekends, 3) temperature change of 0.35 °C in winter is larger than that of 0.32 °C in summer. Increased air temperature over the land area by VH correlates with urban area fraction and building height positively, but not the aspect ratio. The statistically significant VH impact (90% confidence level) has the broadest spatial coverage in Hong Kong shortly after rush hours. The relative VH impact compared to building heat demonstrates the dominative role of vehicle heat in warming low urbanized areas with highways and circulation roads. The spatiotemporal distributions of the VH impact provide insights into the potential benefits of green transportation technology and policy in mitigating urban heat islands.

Pressure Test Systems

A Bench Test for an Electric Vehicle's Heating and Cooling System Reveals how Power Consumption and Performance Changes Over its Life

Development of portable measuring system for testing of electrical vehicle's heat energy recovery system

Nowadays the consumer society applies a huge amount of energy in many fields including transportation sector. Internal combustion vehicles contribute substantially to the air pollution. An alternative solution for reducing energy consumption is replacing the internal combustion vehicles by electrical or hybrid vehicles. Today one of the biggest disadvantages of the electrical vehicles is the finite capacity of batteries. The research topic presented in this paper is the „Energy Harvesting”, and development of energy recovery system for electrical vehicles which largely contributes in increasing the driving range. At the current phase of the research efficiency analysis of the heat energy recovery devices are investigated in real driving circumstances. Computer based mobile and wireless measurement system for the analysis was developed, tested and installed in a real vehicle. Driving tests were performed and analysed in different circumstances.